The present invention relates to a method and a device for fault location in a medium-voltage network according to FIG. 1. In the following description, a medium-voltage network will be referred to as an MV network. An MV network comprises a number of lines, which may each, in turn, branch off into a number of branch lines. The lines are supplied from MV switchgear 1 in an MV station. The MV switchgear is supplied via a transformer 2 from high-voltage switchgear 3. In an installation where the invention will be used, measurement of the common supply voltage and sum voltage of the lines is performed with the measuring devices 4 and 5 in the MV station, where also a so-called fault locator 6 is located.
Fault location in the MV network is normally an integral part of superordinate protection systems relating to faults on circuit breakers, contactors, relays etc. With the aid of various protection, monitoring and so-called expert systems, the faulty line may be determined.
By means of a method and a device according to the invention, determination of the distance to the fault on the faulty line may be performed with the aid of the values of voltage and the sum current of the lines, measured in the MV station.
The principle of distance determination according to the invention is particularly useful for cable networks but may also advantageously be used for overhead line networks.